Spark plug for internal combustion engines



F. lGNATJEv 2,894,162 SPARK PLUG'- FoR nnfzmmLv coMBUsTIoN ENGINES July 7, 1959 INVENTOR.

9 MAZ United States Patent@ M' b b 2,894,162` n SPARK PLUG ron INTERNAL coMBUsrroN i ENGINES 4Feodor Ignatjev, East Norwalk, Conn. Y Application November 18, 1957, Serial NoT 697,192 i 4 claims. (ci. 31a- 141)` `application relates to an electrical igniting device such as a. spark plug as employed for igniting the airgas mixture `in the `combustion chamber of `an internal combustioii` engine, the invention more particularly relating to anfmproved structural form and relative physical arrangement in the electrode elements of the device.

"y 'Thel conventional form of sparkplug now employed in `internal `combustionyengines comprises, basically, a shell `or casing having a cylindrical fitting which is threaded to permit the plugto `be removably inserted` in the cylinder head'of `an engine. Disposed centrally ofthe `shell is` an electrode surrounded by insulating means, both ends of `sa'id` `electrode extending beyond the insulating means with Vone end disposed within the combustion chamber` and ofthe plug, which together with the central electrode n 'defines a spark gap, extends radially from theshell of the plug to a position `spaced `from said insulated electrode. Saidother electrode is electrically connected to the shell of the plug and serves as a ground for the high voltage circuit which runs through theshell of the plug to the body of the engine itself. The central electrode will here- `inafter also be referred to as the source electrode, `and Athe other electrode connected to the shell of the spark plug willbe `hereinafter referred to also as the ground electrode.

It is believed to `be generally recognized that ideal combustion exists only when ignition of the charge starts at `the entire charge. Failure of any portion or areaof the` .are being developed for operating athigher compression l,nijatios-nand at higher temperatures, since at these higher ratios and temperatures there is a greater tendency of the charge or a portion thereof to preignite or detonate. Detonation reduces power output, causes overheating, unduly stresses the cylinder head and the moving parts operating therein and is generally objectionable from the noise and vibration standpoint. Detonation is belived to result from a portion of charge being compressed into a pocket and igniting spontaneously from adiabatic cornpression in advance of the time it would otherwise be ignited according to the ideal progression of the combustion wave front.

It is beileved that one of the factors which has contributed largely to the problem of uneven rate of combustion and consequent uneven pressure on the piston head has been the structural form and disposition of the ground electrode of the spark plug. In the type of plugs most commonly used in automotive engines a single ground electrode is employed, it extending longitudinally from the bore of the plug shell and being bent substan- ICC tally at. right angles so as to extend radially to a point underlying the centreof source electrode at a specied gap distance axially with respect to the source electrode. With this coniiguration, the ground electrode acts as a physical barrier between the spark gap and a large area of the combustion chamber. Consequently, the combustion wave front originating within the spark plug is unable to reach a large` area of `the combustion chamber directly but rather only indirectly because of the physical barrier presented by the ground electrode. Other forms of plugs employ a plurality of ground electrodes, and. this isparticularly prevalent in spark plugs intended for use in aircraft engines, but since a spark will traverse only one gap at atime `the net result of the additional electrodes is to present additional `barriers to the progression of the combustion wave front throughout the entire area of the combustion chamber.

Accordingly, the ground electrode of theplug in accordance with the `present invention is so designed and disposed as to directly expose the greatest possible area of the combustion `chamber to the pointof the spark thereby presenting a minimum barrier to the even and steady progression of the combustion wave front throughout the chamber. This4 is achieved through the use of a single ground electrode which, however, does not underlie the entire tip area of the Source electrode but rather is bifurcated to form electrode tips each having no more than half the cross sectional area of the usual ground electrode, the two tips forming therebetween a gap which permits a greater areaof the combustion chamber to be directly exposed to the spark travelling between one of the tips and the source electrode.

It is therefore an object of the invention to achieve more efficient combustion in an internal combustion engine.

It is a further object of the invention to achieve, through improved electrode design, a more even rate of combustion of a charge within an internal combustion engine.

An additional object of the invention is to provide a spark plug which will directly expose a spark to a greater area of the combustion chamber in which it is located. n

Still further objects of the invention. together with the features contributing thereto and advantages accruing therefrom will be apparent from'the following description when read in conjunction with the drawings where- Fig. 1 is a cross sectional view of the combustion charnber of aninternal combustion engine showing a typical arrangement of `spark plug in relation thereto. `Fig. 2` isan elevation of a spark plug according to the instant invention.`

AFig; 3 is a sectional view `of the spark plug taken along lines 3-3 of Fig.` 2.

Fig. 4 is an enlarged bottom View of the spark plug showing in particular the configuration of the improved ground electrode.

As can be seen in Fig. 1 the head portion of an engine cylinder comprises a combustion chamber which is the area defined by the walls 1 of the cylinder and the upper face of a piston 2 reciprocating within the contines of the cylinder. Combustion of fuel, introduced into the cylinder and compressed in the combustion chamber by the upward thrust of the piston, exerts a downward force on the piston which in tur-n is transmitted through a connecting rod 3 to rotate a crank shaft, not shown. The compressed fuel is ignited through the intermediary of a spark plug 5 which is secured at a suitable location in the cylinder head, the plug being electrically connected to a source of high voltage through an ignition wire 6.

As can be best seen in Figs. 2 and 31, the general construction of the spark plug comprises a supporting body or shell 7 made of a suitable conducting metal and formed in an open and substantially cylindrical shape. The lower extremity or shank Sof the shell is threaded to enable insertion of the plug in a correspondingly threaded opening of the cylinder'head. The upper `portion 9 of the shell is in the form of a multi-faced-nut to facilitate application of a wrench for the purpose ofiriserting'or removing the plug from the cylinder head.

Supported within the shell of 'the plug is an insulator 11 which may be formed of porcelain or the -like, the insulator in turn containing aconductor 12 constituting one of the electrodes of thespark plug. Electrode '12, at each end thereof, projects beyond the contines ofthe insulator 11 with the upper end .of 'the lelectrodebeing yformed with means,.such as threadslor the' like, ,to permit jonder and electrical contact with a suitable 'fitting Provided' on the aforementioned ignition wire 6.

The outer orground electrode v13 is joined'to the bot- -tom face of the shank portion 8 of the plug. and comprises an extrusion of suitable conducting metalbent over to extend inwardly and radially relative to the shank of the plug, the bent over portion of the electrode'being bifurcated, as best seen in Figs. 3 and 4, soas to provide va plurality ofelectrode tips13a, 13b veach defini-ngv a point of a cycle as may be adjusted by distributor mechanism not shown, a spark isi caused to jump betweenthe source electrode 12 and either one ofthe groundelectrode tips 13a, 13b. Under normal conditions the spark alternates between the two ground electrode tips during successive rings of the plug. In view of the alternating tiring of the spark, it will be apparent that eachof the Velectrode tips 13a, 13b need have no more than half the cross sectional area of a conventional non-bifurcated electrode to achieve the same life expectancyof such conventional forrn of electrode. It will vfurther be apparent that the space between the two electrode tips 13a, 13b permits direct exposure of the spark to the area of the combustion fchamber directly beneath the fplug, which is generally the central area kof `the combustion chamber, regardless of which of the twozelectrode Vtips V.is eiective for any one tiring. It willbestill'further apparent that by providing two spaced electrode tips of reduced cross sectional area, one of which in eachiiring `being spaced fromand out of line of the spark, the area portion of the combustion chamber shielded from direct exposure to the spark will be ysubstantially reduced.. @Accordingly, since the tips are spaced apart,` therespective shielded areas of the combustion chamber .will becorrespondingly spaced apart or separated so as to prevent any one substantially large or concentrated area of the combustion chamber from being shielded from the spark as'is the case with the conventional form vof'ground'electrode. As a result, combustion is able to proceed with a more even and uniform wave front throughout the entire larea of the combustion chamber enabling spark timing to be advanced to a more advantageous point of the cycle and thereby generally accomplishing more eflicient combustion with correspondingly increased power outputfrom the cylinder.

While there has beenshown and described herein what is believed to lbe a preferred embodimentofthetinvention, it is obvious that changes in form could be made without departingfrom thelspiritof the invention, and itis,there fore, intended that the invention V.be ynot limited to the exact form herein 'shown and described nor to anything less than the whole of the invention as herenbefore set forth and as hereinafter claimed.

Whatis claimed is: f Y

vl. In a spark plug of the character .describcdfior igniting the .'fuel chargev of an internal combustionengi'ne and having a cylindrical shell of conducting material supporting a longitudinal coaxially disposed electrode I insulated therefrom, a second electrodeconnected.to..said

shell and radially `disposed to complete-a spark circuit with a terminal end of said lirst mentioned electrodeyffsaid second electrode being furcated to form laterallyspaced .electrode tips each longitudinally spaced beyondnd defining -a sparkgap of substantially theisame Awicrlthvvith 'I -said terminal end of the rst mentioned electrode.

v.2..Ina spark plug of the character -describedtfor Uniting the fuel Ycharge of internalI combustion -enginesaand having/a` cylindrical shell of conducting 'fmaterialaadapted ,laterally spaced electrode tips.

4. The invention according to claim 3 whereinlfsaid `laterally spacedelectrode tips lielin opposedrelationi-to the'axis of said source electrode, lsaid tips being'. laterally Volset to the same extent relative to the longitudinal axis of said source electrode.

References Cited in the le of this .patent UNITED STATES PATENTS 1,5 64,645 Thomas `Dec. k8, i 19'2A8 1,912,516 Davis 'June 6,1933 2,469,304 Lukeman May V3, `1949 

